BRCA 1/2
Test Description
Among all cases of breast cancer in women, approximately 5% to 10% involve a
hereditary form of the disease. Most of these hereditary cases are due to mutations
in breast cancer (BRCA 1 or BRCA 2) genes. There is a higher risk of these mutations
in Eastern European Jewish women. These mutations are also associated with
increased risk of ovarian cancer in women and breast cancer in men. Women with
altered BRCA 1 or 2 genes have a lifetime risk for developing breast cancer of up
to 85% (compared to 13% for women without BRCA mutations). Ovarian cancer
risk is up to 60% compared to 2% in the general population.
BRCA genes are present in all cells of the body. Proteins of the BRCA genes
affect only breast and ovarian tissue. The test involves checking a sample of DNA
from white blood cells for the presence of BRCA mutations. Individuals considering
undergoing this test should not do so lightly. Counseling should be offered regarding
what test results will mean, what options are available for prevention of cancer,
and the ramifications of having the test information in the medical record. However,
the testing should be considered for women with close male/female relatives with
breast cancer or female relatives with ovarian cancer. This is especially important
if the cancer was diagnosed before age 50. Some individuals with positive test
results may choose to have prophylactic surgery, although this does not guarantee
that the cancer will not appear in remaining tissue. Due to the high risk of breast
cancer in these women, consideration might be given to adding breast magnetic
resonance imaging (MRI) to mammography for cancer screening; however, riskbenefit,
and cost analysis is needed
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.THE EVIDENCE FOR PRACTICE
• The USPSTF recommends against routine referral for genetic counseling or routine
breast cancer susceptibility genes (BRCA) testing for women whose family history is not
associated with an increased risk for deleterious mutations in breast cancer susceptibility
gene 1 (BRCA1) or breast cancer susceptibility gene 2 (BRCA2).
• The USPSTF recommends that women whose family history is associated with an
increased risk for deleterious mutations in BRCA1 or BRCA2 genes be referred for genetic
counseling and evaluation for BRCA testing.
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Normal Values
Normal BRCA genes
Possible Meanings of Abnormal Values
Positive Negative
Increased risk of developing breast Not at risk for hereditary breast cancer due
and/or ovarian cancer to BRCA mutations (can developother types)
other types)
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Interventions/Implications
Pretest
• Explain to the patient the purpose of the test and the need for a blood sample to be drawn.
• No fasting is required before the test.
Procedure
• A 7-mL blood sample is drawn in a red-top collection tube.
• Gloves are worn throughout the procedure.
Posttest
• Apply pressure at venipuncture site. Apply dressing, periodically assessing for continued
bleeding.
• Label the specimen and transport it to the laboratory.
• Report abnormal findings to the primary care provider
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Clinical alert
• Patients considering BRCA testing should receive pretest counseling to discuss the
possible ramifications of having genetic information in their medical record.
• Individuals with positive BRCA mutations should receive counseling regarding
surveillance and risk avoidance.
تعليقات
إرسال تعليق